Bolster chair

ABSTRACT

A bolster chair particularly for metalwork support in reinforced concrete but which is not subject to weathering, wherein a steel strengthening continuous bar is completely encased by a plastic section which includes integral feet of plastic. Locating protruberances may be placed along the length of the plastic section and the feet may be triangular, of great stability, with reinforcing shoulder portions extending longitudinally of the plastic section.

Unite 1 States Patent 1191 Vl'lgh 1 1 Oct. 8, 1974 [54] BOLSTER CHAIR 3,167,882 2/1965 Abbott 52/309 x 3,209,509 10/1965 O'Callaghan 52/688 [76] lnvemor- Sand" 214 Nantucket Blvd 3,488,907 1/1970 Aberg 52/689 x scabol'o Oman), Canada 3,529,392 9 1970 Adams 52/687 [22] Filed: May 9, 1972 Primary Examiner-Henry C. Sutherland {21] App]. No.: 251,797 Assistant ExaminerCarl D. Friedman Attorney, Agent, or Firm-D. Paul Weaver [30] Foreign Application Priority Data Apr. 4, 1972 Canada 138845 [57] ABSTRACT A bolster chair particularly for metalwork support in [52] U.S. Cl 52/687, 52/309, 52/740 reinforced concrete but which s not subject to weath- [51] Int. Cl. E04c 5/16 fi g, wherein a steel strengthening o nuous bar is [58] Field of Search 52/677-689, completely enca y a plastic ction which includes 52/515, 727, 309 integral feet of plastic. Locating protruberances may be placed along the length of the plastic section and [56] References Cit d the feet may be triangular, of great stability, with rein- UNITED STATES PATENTS forcing shoulder portions extending longitudinally of 2,312,293 2/1943 Weiss 52 727 x the plast'c Sectlon' 3. 2,992,131 7/1961 Bricknell 52/727 X 1 Claim, 3 Drawing Figures BOLSTER CHAIR This invention relates to supporting members for reinforcing rods in concrete moulding and form work.

It is well known that for best protection from the weather, steel reinforcing rods and metalwork to be introduced into concrete should be spaced from the edge of any part of the exposed finished product so that they are completely protected by a concrete covering. Nevertheless, in order for the best tensile support to be provided by such reinforcing rods and metalwork, they should be as close as conveniently possible to the edges of the finished product.

These mutually antagonistic requirements are compromised by the use of spacers set against the mould walls which support the metalwork concerned.

Individual type spacers or chairs are well known in the art, which are fastened, to the mould formwork or metalwork before the concrete is poured, and to the reinforcing rods. Other types of spacers, particularly at the bottoms of moulds or formwork, are attached to the reinforcing metalwork such as by snapping onto a rod and have feet which rest against the formwork. Still other spacers are of the bolster type which form a continuous support for rods fastened transversely to them.

Bolster chairs being larger and being required to supply continuous support have to be very much stronger than simple single spacers. As a consequence even though simple spacers can be made of plastic material, it is necessary that practical bolster chairs be made of steel. Thus although spacers of plastic which are inert to the weather are known, bolster chairs present a very real weathering problem.

The exposed metalwork of the bolster chair protrudes to the exterior of the finished reinforced concrete even though the reinforcing rods are properly contained within the concrete mass. These metallic members then provide rust sources which in a short while cause, the untreated surfaces of concrete to look unsightly, and subsequently allow a channel for water ingress to the reinforcing metal structure and subse quent weakening of the entire unit. Thus the consequences of the exposed reinforcing rods again appear.

Efforts have been made to tip the feet of bolster chairs in plastic by dipping the finished chair in a melt of the plastic so that a protective cap is formed over each foot, but this is expensive in being a completely different handling and treating step in the manufacture of the chairs.

The present invention is particularly satisfactory in overcoming these problems of the art since it can be made inexpensively, is completely rust resistant and is extremely strong. In accordance with the invention a bolster chair and a method and apparatus for its construction are provided in which a bolster chair for metalwork support comprises a plastic elongated section, plastic feet integrally molded with said section at spaced intervals along said section, said feet including means preventing displacement of said feet both in a longitudinal and in a transverse direction of said rod and a load supporting continuous strengthening bar integrally surrounded by said section rod and enclosed by said plastic. Preferably, the rod is of strong metal or steel, locating protruberances are spaced along the length of the plastic section for locating reinforcing metalwork and the feet comprise triangular wing portions with reinforcing shoulder webs extending longitudinally of the plastic section.

The invention will now be described with reference to the accompanying drawings in which:

FIG. 1 shows a partly sectional perspective view of a section of the finished article,

FIG. 2 shows a method of formation, and

FIG. 3 shows a side view of one embodiment of the finished article before severing.

The bolster chair of FIG. 1 consists of a transverse section 1 for supporting concrete reinforcing metalwork along which locating protrubcrances 2 are arranged suitably at about inch intervals. The rod is supported by a series of feet 3 arranged at convenient positions along the rod typically at 4 /5 or 5 5 inch spacing (with the protruberance spacing mentioned above). The feet comprise triangular wing members 4 integrally moulded with the section 1 and strengthened by shoulder webs 5 extending lomgitudinally of the section 1 and attached to the underside of section 1 and to the faces of the wings 4. Integrally molded with the wing members 4 is a head portion 6 which provides additional thickness to the section 1 at the point of junction of the feet and also serves as a locating protruberance in conjunction with protruberances 2. To provide for extreme strength of the bolster chair, a steel rod 10 is integrally enclosed within the section 1.

The complete encasing of rod 10 by the plastic provides strong bonding between the plastic and the rod 10, and prevents any exposure of the rod. The overall strength developed provides support for reinforcing bars with little or no deflection of the bolster chair. The lower edges 11 of the wings 4 rest on the formwork in which the concrete is to be cast and since the feet 3 are entirely of a plastic material, no rusting or weathering problems occur.

These bolster chairs can be provided in any length, five foot being a commonly acceptable length.

The apparatus for manufacturing this bolster is shown in diagrammatic form in FIG. 2 and includes a reel 20 carrying steel rod 21 fed endwise into the working space 23 of a mold 24. Only one half of the mold is shown in the FIG. 2 consisting of a cavity 25 which when mated with anidentical cavity of a second mould half approaching from above the plane of the paper will form an enclosed cavity space into which plastic material can be injected in molten state. The rod 21 isled into the mould space in coaxial position in the central bore 30 at one end by the rollers 22. At the other end a suitable conveyor means 31 supports the bottom edge 11 of a previously formed foot. When the mould is closed therefore, liquid thermoplastic is injected into the cavity 25 and is prevented from escaping from the end 32 which is obturated by the previously formed end 33 of the section of bolster shown on conveyor 31. At the other end 34 the mould lips 35, which close onto and retain the rod 21, also prevent escape of molten plastic. When the plastic formed around the rod within the mould has cooled sufficiently, it is released from the mould in conventional manner by ejector pins (now shown) and the mould halves are retracted upwardly and downwardly respectively from the plane of the paper. The rollers 22 then advance the rod so that the newly formed section is moved onto conveyor 31 and the rod is positioned in the mould for a subsequent moulding as that just described. It is clear that this process can be continued indefinitely, subject to space limitations for take-up of the finished bolsters, and the continuous section severed to the length required. Such severance will expose rod at the end, but this is of little concern since it would be adjacent an edge face rather than a bottom face of the completed concrete structure and normally would be spaced inwardly from the edge face in any event.

On embodiment of the finihsed article before severing from the rod 21 is shown in FIG. 3. In this embodiment which typically is of five foot length with spacing between feet 3 of about four inches the entire five foot section is moulded with plastic in one action. Thus to effect this single moulding action the mould corresponding to mould 24 of HO. 2 would be of the full five foot length otherwise the process would be the same as described for FIG. 2.

It is clear that the bolster of this invention can be varied in structure by altering spacing of the feet or the locating protruberances 2 and by variation of the size or cross section of the steel rod for special requirements. The feet too may be differently shaped as required. The particular structure described here, however, is simple, strong, economical in the use of both steel and plastic and extremely stable against overturning and displacement.

I claim:

1. A bolter chair for concrete reinforcing bars comprising a steel bolster bar, a plastic sleeve element molded integrally on the bolster bar and being coextensi ve therewith and completely enclosing the bolster bar, spaced plastic protuberances integrally molded on at least the upper side of said plastic sleeve for use in locating reinforcing bars resting on the bolster chair, and plastic spacer feet integrally molded on said sleeve at longitudinally spaced intervals thereon and depending therefrom, said spacer feet being of equal heights and being of triangular configuration and disposed in planes normal to the bolster bar and sleeve, said spacer feet projecting equidistantly from opposite sides of the bolster bar and having their triangular base edges disposed in a common plane, and shoulder webs molded integrally with the underside of said sleeve and the oposite vertical faces of said triangular spacer feet and lying in a plane perpendicular to the spacer feet and passing through the axial center line of the bolster bar, said plastic sleeve being fixed on and highly resistant to movement on the bolster bar and the spacer feet being fixed on said sleeve and forming a rigid unit therewith. l 

1. A bolter chair for concrete reinforcing bars comprising a steel bolster bar, a plastic sleeve element molded integrally on the bolster bar and being coextensive therewith and completely enclosing the bolster bar, spaced plastic protuberances integrally molded on at least the upper side of said plastic sleeve for use in locating reinforcing bars resting on the bolster chair, and plastic spacer feet integrally molded on said sleeve at longitudinally spaced intervals thereon and depending therefrom, said spacer feet being of equal heights and being of triangular configuration and disposed in planes normal to the bolster bar and sleeve, said spacer feet projecting equidistantly from opposite sides of the bolster bar and having their triangular base edges disposed in a common plane, and shoulder webs molded integrally with the underside of said sleeve and the oposite vertical faces of said triangular spacer feet and lying in a plane perpendicular to the spacer feet and passing through the axial center line of the bolster bar, said plastic sleeve being fixed on and highly resistant to movement on the bolster bar and the spacer feet being fixed on said sleeve and forming a rigid unit therewith. 